Allow using non-system fonts from files with BFont

[calvinb]

BFont can only work with fonts installed into the system (packaged/non-packaged). It would be nice to be able to load external fonts from the filesystem.

Use case: private fonts for applications/games not relevant to the rest of the system, applications like font previewers/installers, web browsers with @font-face.

[dsizzle]

I posted a review patch to Gerrit: ​https://review.haiku-os.org/c/haiku/+/4790

I'm not positive this is the correct approach, and welcome all comments and criticisms!!

it's barely tested but I wanted to make sure I wasn't heading the wrong direction.

[pulkomandy]

Patch merged in hrev56649. It seems it was not included in beta4, should we do that or is it too risky?

[waddlesplash]

Too risky for now. Let's hold off and merge it later, after it's been well-tested.

[madmax]

How about just the interface in BFont (and maybe ServerProtocol) with the implementation returning an error?

[dsizzle]

I'm not sure what the benefit of adding just the interface would be.

The risky part, in my opinion, isn't the new font loading, but rather the fact that the global font manager was refactored. If the new font loading is broken it's not a big deal, but if the core font handling turns out to be broken that would be a real shame for beta4.

[pulkomandy]

Adding just the interface will allow building the new haikuwebkit releases with beta4 buildbots, even if they can't display custom fonts on beta4. So I can continue making regular haikuwebkit releases